This invention relates to a method for manufacturing a flame-retardant polyurethane foam, more particularly to a method for manufacturing a flame-retardant polyurethane foam which generates no poisonous gas at its preparing process and causes no corrosion of a surface material, a material to be adhered and the like, and when the method is employed for flame laminates, a cured product having excellent flame retardant and adhesion characteristics could be obtained.
Heretofore, a flame-retardant polyurethane foam has been used in many fields such as cushion materials of automobiles, beds, sofas and the like and other fields. These polyurethane foams have been employed in many kinds of uses such as for general-purpose blowing, integral blowing, high-frequency wave welder, flame laminate, general-purpose slub urethane or the like.
As a method for manufacturing this kind of the flame-retardant polyurethane foam, there have been known a method which employs, as a flame retarder, an inorganic compound such as a boron compound, aluminum hydroxide, antimony trioxide or the like and is carried out by reacting the starting materials by the one-step method or the prepolymer method; a method which is carried out by the same manner as mentioned above except for using a halogen compound such as polychloroparaffin as a flame retarder; and a method which is carried out by the same manner as mentioned above except for using a halogen-containing phosphate such as tris(chloroethyl)phosphate, tris(2,3-dichloropropyl)phosphate and the like as a flame retarder.
However, in the method of employing the inorganic compound as a flame retarder, it is not suitable for the flame laminate processing, etc. since the inorganic compounds accelerate carbanization of the polyurethane foam. Further it has an problem that it is necessary to select an inorganic compound appropriately because the inorganic compound reacts with a catalyst for blowing so that the desired polyurethane foam could not be obtained.
On the other hand, in the case of a manufacturing method using the halogen compound or the halogen-containing phosphate as a flame retarder, when preparing a polyurethane foam, the methods have a problem that they generate poisonous hydrogen halide gas as evaporates or cracked gas because the temperature of the blowing process becomes high, i.e. 100.degree. C. or more. Further, after manufacturing, since the prepared polyurethane foam release a hydrogen halide gas gradually, the generated hydrogen halide made the surface material colored or physical properties of the polyurethane foam lowered, whereby there is a problem in the point of durability. Moreover, when the above polyurethane foam is used as the polyurethane foam for a high-frequency wave welder or a flame laminate, there are problems that a hydrogen halide gas is generated because of heat treatment at the manufacturing process to cause difficulty in operation as well as to corrode a material to be adhered.